A kind of Utkālika Śruta (a category of Āgamas (canonical works), which is allowed to be studied at all time barring the akāla prahara (i.e., the period in which the study of Āgamas is prohibited)).
kālavelāvarjaṃ paṭhyate tadūrdhvaṃ kālikādityutkālikam.
(Sthā 2.106 Vṛ Pa 48)